The Role of FeO in Creating of Multilevel Structure of the Surface Layer of Metallic Materials in the Dry Slip Zone under Electric Current of High Density

Dry sliding of powder composites of Cu-Fe (steel)-graphite compositions against grinded steel surface in the wear-in stage under high-density electric current (higher 100 A/cm(2)) was carried out. It was shown that electrical contact occurred at individual points on the sliding surface of the counterbody. Pittings were observed at these points. This type of sliding electrical contact had low electrical conductivity. It was established by visual observations that the sliding of these composites for 2-3 hours led to the appearance of patch-like FeO film on the sliding surface. An increase in the area of this film corresponded to an increase in the contact electrical conductivity and wear resistance. The formation of tribolayer in the composites friction zone occurred during sliding. It was found by X-ray analysis that the tribolayer contained FeO, Cu and alpha-Fe. This indicated the composite-like structure of tribolayer. Using Auger spectrometry it was found that the atomic content of FeO could exceed half of the atoms on the sliding surface of some composites. Such high FeO content in the tribolayer was often accompanied by melting of the friction surface. Such tribolayer structure made it possible to perform multilevel stress relaxation and achieve high wear resistance and electrical conductivity of the contact. The impossibility of the emergence of a multilevel structure of the (primary structure + tribolayer) type due to the low FeO content in the tribolayer was accompanied by the presence of more than 50 at % Cu on the sliding surface and adhesion in the contact zone. This has led to low wear resistance and electrical conductivity of the contact.